Magnetic catalyst composition for hydroformylation of olefins

ABSTRACT

A functionalized nanomaterial having an average particles size of less than 10 nm comprising an iron oxide nanoparticle core and a bis(diarylphosphinomethyl) dopamine based ligand layer anchored to the iron oxide nanoparticle core is disclosed. In addition, a catalyst composition for use in a variety of chemical transformations wherein the bisphosphine groups of the functionalized nanomaterial chelate a catalytic metal is disclosed. In addition, a method for producing the functionalized nanomaterial and a method for the hydroformylation of olefins to aldehydes employing the functionalized nanomaterial with high conversion percentage and high selectivity are disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of Ser. No. 14/989,219,now allowed, filed on Jan. 6, 2016.

BACKGROUND OF THE INVENTION

Technical Field

The present disclosure relates to a functionalized nanomaterialcomprising bis(diarylphosphinomethyl) dopamine based ligands anchored toiron oxide nanoparticles. Additionally, the present disclosure relatesto methods for producing the functionalized nanomaterial and itsapplication to chelate catalytic metals and catalyze chemicaltransformations involving those catalytic metals including thehydroformylation of olefins to aldehydes.

Description of the Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Aldehydes can be converted into a number of useful chemicals viacondensation, hydrogenation, amination, etc. The catalyzedhydroformylation reaction is of significant commercial importance in theproduction of aldehydes from aliphatic as well as substituted aromaticolefins via syngas-mediated reactions. Approximately 11 million metrictons of oxo chemicals are produced and consumed per year worldwide withan annual growth rate of 4%. [S. K. Sharma and R. V. Jasra, Catal.Today, 2015, 247, 70.—incorporated herein by reference in its entirety].Homogeneous catalytic processes have been extensively used for thealkene to aldehyde conversion [C. Claver, P. Kalack, L. A. Oro, M. T.Pinillos and Cristina Tejel, Journal of molecular Catalysts, 1987, 43,1; A. Orejon, C. Claver, L. A. Oro, A. Elduque and M. T. Pinillos,Journal of Molecular Catalysis A: Chemical 1998, 136, 279; A. B. Rivas,J. J. Pérez-Torrente, A. J. Pardey, A. M. Masdeu-Bultó, MontserratDiéguez and Luis A. Oro, Journal of Molecular Catalysis A: Chemical2009, 300, 121; J. Norinder, C. Rodrigues, A. Börner, Journal ofMolecular Catalysis A: Chemical 2014, 391, 139; M. Jouffroy, R.Gramage-Doria, D. Armspach, D. Semeril, W. Oberhauser, D. Matt, and L.Toupet, Angew. Chem. Int. Ed. 2014, 53, 3937; L. C. Matsinha, S. F.Mapolie, and G. S. Smith, Dalton Trans., 2015, 44, 1240; P. Dydio, R. J.Detz, B. D. Bruin, and J. N. H. Reek, J. Am. Chem. Soc. 2014, 136, 8418;T. T. Adint and C. R. Landis, J. Am. Chem. Soc. 2014, 136, 7943; L. Wu,I. Fleischer, R. Jackstell, I. Profir, R. Franke, and Matthias Beller,J. Am. Chem. Soc. 2013, 135, 14306; and Z. Nairoukh, J. Blum, Journal ofMolecular Catalysis A: Chemical 2012, 358, 129—each incorporated hereinby reference in its entirety]. However, the challenges in separation areparamount and the cost of separation is prohibitively high in terms ofthe need to use fairly expensive chemicals and fairly large amounts ofprecious metals.

In the past two decades, great efforts have been devoted towarddeveloping alternatives to homogeneous catalysis to minimize theseparation cost and maximize the product purity. Heterogeneous catalysisoffers the ease of separation and reusability. Moreover, it minimizesthe use of environmentally toxic solvents needed in large quantities forseparation and purification [V. Polshettiwar and R. S. Varma, GreenChem., 2010, 12, 743.—incorporated herein by reference in its entirety].Most of the heterogeneous catalysts are supported on solids such assilica [V. Polshettiwar, B. Baruwati and R. S. Varma, Chem. Commun.,2009, 1837; K. Nozaki, Y. Itoi, F. Shibahara, E. Shirakawa, T. Ohta, H.Takaya and T. Hiyama, J. Am. Chem. Soc. 1998, 120, 4051; S. Ricken, P.W. Osinski, P. Eilbracht and R. Haag, J. Mol. Catal. A Chem. 2006, 257,78; R. S. Varma, Pure Appl. Chem., 2013, 85, 1703; and A. R. McDonald,C. Muller, D. Vogt, G. P. M. van Klink and G. van Koten, Green Chem.,2008, 10, 424—each incorporated herein by reference in its entirety].Silica is highly stable, robust and easy to functionalize; organicfunctional groups can be easily anchored via either covalent bonding oradsorption on the surface to provide catalytic centers [A. S. Kumar, M.A. Reddy, M. Knorn, O. Reiser, and B. Sreedhar, Eur. J. Org. Chem. 2013,4674.—incorporated herein by reference in its entirety]. However, inmost of the cases, a great number of catalytic sites are buried withinthe solid support, thereby resulting in a decrease in the overallreactivity. Leaching out of the catalyst by the cleavage of bondsbetween metal and ligand also hinders the ease of separation.

Due to their robustness and high surface area, nanoparticles have becomefavorable catalyst support systems [R. Abu-Reziq, H. Alper, D. Wang, andMichael L. Post, J. Am. Chem. Soc. 2013, 128, 5279; and J. P. K.Reynhardt, Y. Yang, A. Sayari and H. Alper, Adv. Synth. Catal. 2005,347, 1379—each incorporated herein by reference in its entirety]; atnanoscale, the catalyst center may be more exposed to the reactant,thereby enhancing the activity. In this regard, superparamagnetic ironoxide nanoparticles (SPIONs) offer a promising research strategy todevelop surface coated recyclable catalysts by anchoring homogeneousorganic species (ligand or metal complexes) on the heterogeneous system,thus combining the advantages of both of the systems. In this context, adendritic hydroformylation catalyst with excellent reactivity andselectivity attributes has recently been reported [R. Abu-Reziq, H.Alper, D. Wang, and Michael L. Post, J. Am. Chem. Soc. 2013, 128,5279.—incorporated herein by reference in its entirety]. For thesepurposes, the chelating ligand, bis(diphenylphosphinomethyl) amine hasproven itself for its interesting nature of coordination modes withdifferent transition metals and its wide range of catalytic applications[T. T. Co and T.-J. Kim, Chem. Commun., 2006, 3537—incorporated hereinby reference in its entirety].

In view of the forgoing, one object of the present disclosure is toprovide novel functionalized nanomaterials comprising bisphosphinateddopamine (bpd) based ligands anchored on nanostructured magneticnanoparticles. A further aim of the present disclosure is to provide aneconomical and robust process for synthesizing and characterizing theproduced functionalized nanomaterials. An additional aim of the presentdisclosure is to provide applications of the functionalizednanomaterials as recyclable and thermally stable catalysts once chelatedwith a catalytic metal in a wide variety of chemical transformationssuch as the conversion of olefins to aldehydes by hydroformylation usingrhodium as the catalytic metal center.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect, the present disclosure relates to afunctionalized nanomaterial comprising i) an iron oxide nanoparticlecore and ii) a bis(diarylphosphinomethyl) dopamine ligand, wherein thebis(diarylphosphinomethyl) dopamine ligand is anchored to a surface ofthe iron oxide nanoparticle core by phenolic hydroxide groups to form abis(diarylphosphinomethyl) dopamine ligand layer and wherein thebisphosphine groups of the bis(diarylphosphinomethyl) dopamine ligandchelate a catalytic metal.

In one embodiment, the functionalized nanomaterial is in the form ofparticles having a spherical morphology and an average diameter of 1-20nm.

In one embodiment, the functionalized nanomaterial has a phosphinecontent of 0.2-1.0 mmol of phosphine per gram of functionalizednanomaterial.

In one embodiment, the average thickness of thebis(diarylphosphinomethyl) dopamine ligand layer is less than 5 nm.

In one embodiment, the bis(diarylphosphinomethyl) dopamine ligand layercovers greater than 70% of the surface of the iron oxide nanoparticlecore.

In one embodiment, the iron oxide nanoparticle core comprises magnetite,Fe₃O₄. In one embodiment, the bis(diarylphosphinomethyl) dopamine ligandis bis(diphenylphosphinomethyl) dopamine.

In one embodiment, the functionalized nanomaterial loses less than 1% ofits total weight after heating at a temperature of 200° C. and less than10% of its total weight after heating at a temperature of 500° C.

According to a second aspect, the present disclosure relates to aprocess for producing the functionalized nanomaterial in any of itsembodiments comprising i) reacting paraformaldehyde with a phosphine toproduce a phosphinomethanol ii) reacting the phosphinomethanol with adopamine salt to form the bis(diarylphosphinomethyl) dopamine ligand andiii) mixing the bis(diarylphosphinomethyl) dopamine ligand with the ironoxide nanoparticle core to form the functionalized nanomaterial.

In one embodiment, the iron oxide nanoparticle core is formed byprecipitating an iron salt under alkaline conditions.

According to a third aspect, the present disclosure relates to a methodfor hydroformylating an olefin to a corresponding aldehyde comprising i)mixing the functionalized nanomaterial with the olefin ii) adding arhodium salt as source of the catalytic metal and iii) hydroformylatingthe olefin in the presence of carbon monoxide or a carbon monoxidesurrogate to form the corresponding aldehyde.

In one embodiment, the method further comprises recovering and reusingthe functionalized nanomaterial in at least 2 reaction iterations.

In one embodiment, the rhodium salt comprises rhodium (III) chloride,RhCl₃ or 2,5-norbornadiene-rhodium (I) chloride dimer, [Rh(NBD)Cl]₂.

In one embodiment, the olefin is a styrene.

In one embodiment, a percent conversion from the olefin to thecorresponding aldehyde is greater than 90%.

In one embodiment, the mixing involves no more than 50 mg offunctionalized nanomaterial per 1.0 mmol of olefin.

In one embodiment, the corresponding aldehyde has a linear aldehyde formand a branched aldehyde form and the ratio of the linear aldehyde formto the branched aldehyde form is greater than or equal to 1.

According to a fourth aspect, the present disclosure relates to acatalyst composition comprising the functionalized nanomaterial and acatalytic metal, wherein the bisphosphine groups of thebis(diarylphosphinomethyl) dopamine ligand of the functionalizednanomaterial chelate the catalytic metal.

In one embodiment, the catalytic metal is at least one selected from thegroup consisting of nickel, platinum, palladium, rhodium, iron, gold,silver, ruthenium and iridium.

In one embodiment, the catalyst composition is employed in at least onechemical transformation selected from the group consisting ofhydrogenations, palladium-catalyzed coupling reactions and selectiveoxidations.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is chemical reaction scheme for the synthesis of the iron oxidenanoparticle core wherein (I) is a source of Fe²⁺ such as FeCl₂, (II) isa source of Fe³⁺ such as FeCl₃, and (III) is the iron oxide nanoparticlecore.

FIG. 2 is a chemical reaction scheme for the synthesis of thefunctionalized nanomaterial wherein (IV) is paraformaldehyde, (V) is aphosphine, (VI) is a dopamine based salt, (VII) is thebis(diarylphophinomethyl) dopamine based ligand, (III) is the iron oxidenanoparticle core, and (VIII) is the prepared functionalizednanomaterial.

FIG. 3A is a scanning electron microscopy (SEM) image of the preparedfunctionalized nanomaterial.

FIG. 3B is a transmission electron microscopy (TEM) image of theprepared functionalized nanomaterial.

FIG. 3C is a TEM image of the prepared functionalized nanomaterialparticulates demonstrating a 2 nm thickness of thebis(diarylphosphinomethyl) dopamine based ligand layer.

FIG. 3D is a TEM image of the magnified view of the preparedfunctionalized nanomaterial particulates demonstrating a 2 nm thicknessof the bis(diarylphosphinomethyl) dopamine based ligand layer.

FIG. 3E is a high-resolution transmission electron microscopy (HRTEM)image of selected prepared functionalized nanomaterial particles.

FIG. 3F is a HRTEM image of the magnified view of a selected preparedfunctionalized nanomaterial particle.

FIG. 4 is an X-ray diffraction (XRD) analysis wherein (A) is the XRDanalysis of magnetite, Fe₃O₄, and (B) is the XRD analysis of theprepared functionalized nanomaterial.

FIG. 5 is a Fourier transform infrared spectroscopy (FT-IR) analysiswherein (A) is the FT-IR analysis of bis(methyldiphenylphosphino)dopamine, (B) is the FT-IR analysis of magnetite, Fe₃O₄, and (C) is theFT-IR analysis of the prepared functionalized nanomaterial.

FIG. 6 is a thermal gravimetric analysis (TGA) of the preparedfunctionalized nanomaterial under argon atmosphere at a heating rate of10° C./min.

FIG. 7 is a ¹H nuclear magnetic resonance (NMR) spectra of the preparedbis(diarylphosphinomethyl) dopamine based ligand which isbis(diphenylphosphinomethyl) dopamine in DMSO-d₆.

FIG. 8 is a ³¹P NMR spectra of the prepared bis(diarylphosphinomethyl)dopamine based ligand which is bis(diphenylphosphinomethyl) dopamine inDMSO-d₆.

FIG. 9 is the magnetization-field (M-H) curves for the iron oxidenanoparticle core and the prepared functionalized nanomaterial recordedat room temperature.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring now to the drawings, wherein, like reference numeralsdesignate identical or corresponding parts throughout the several views.

According to a first aspect, the present disclosure relates to afunctionalized nanomaterial including an iron oxide nanoparticle core.Iron oxides are chemical compounds composed of iron and oxygen. Ironoxides are widely used and typically colored yellow, orange, red, brownor black. There are sixteen known iron oxides and oxyhydroxides. Theoxides include iron (II) oxide (wustite, FeO), iron (II,III) oxide(magnetite, Fe₃O₄), Fe₄O₅, Fe₄O₃, and iron (III) oxide including thealpha phase (hematite, α-Fe₂O₃), beta phase (β-Fe₂O₃), gamma phase(maghemite, γ-Fe₂O₃) and epsilon phase (ε-Fe₂O₃). The hydroxides includeiron (II) hydroxide (Fe(OH)₂) and iron (III) hydroxide (bernalite,Fe(OH)₃). The oxide/hydroxides include goethite (α-FeOOH), akaganeite(β-FeOOH), feroxyhyte (δ-FeOOH), ferrihydrite (Fe₅HO₈.4H₂O approx. or5Fe₂O₃.H₂O, better recast as FeOOH.0.4H₂O), high pressure FeOOH,Schertmannite (ideally Fe₈O₈(OH)₆(SO).nH₂O or Fe³⁺₁₆O₁₆(OH,SO₄)₁₂₋₁₃.10-12H₂O) and green rust (Fe^(III) _(x)Fe^(II) _(y)(OH)_(3x+2y−z)(A⁻)_(z) where A⁻ is Cl⁻ or 0.5SO₄ ²⁻). In terms of thepresent disclosure, the iron oxide nanoparticle core may comprise any ofthe known iron oxides or oxyhydroxides above and mixtures thereof.

Iron (III) oxide or ferric oxide is the inorganic compound with formulaFe₂O₃. It is one of the three main oxides of iron, the other two beingiron (II) oxide (FeO) which is rare, and iron (II,III) oxide (Fe₃O₄)which also occurs naturally as the mineral magnetite. Fe₂O₃ isferromagnetic, dark red and readily attacked by acids. Fe₂O₃ can beobtained in various polymorphs. In the major polymorphs, α and γ, ironadopts an octahedral coordination geometry, each Fe center is bound tosix oxygen ligands. α-Fe₂O₃ has the rhombohedral corundum (α-Al₂O₃)structure and is the most common form. It occurs naturally as themineral hematite which is mined as the main ore of iron. γ-Fe₂O₃ has acubic structure, is metastable and converted to the alpha phase at hightemperatures. It is also ferromagnetic. Several other phases have beenidentified, including the β-phase, which is cubic body centered,metastable, and at temperatures above 500° C. converts to alpha phase,and the epsilon phase, which is rhombic, and shows propertiesintermediate between alpha and gamma phase. This phase is alsometastable, transforming to the alpha phase between 500 and 750° C.Additionally, at high pressure an iron oxide can exist in an amorphousform. The iron oxide in the iron oxide nanoparticle core may be iron(III) oxide and may have an α polymorph, a β polymorph, a γ polymorph, aε polymorph or mixtures thereof.

Iron (II, III) oxide or magnetite is another main oxide of iron withformula Fe₃O₄. It contains both Fe²⁺ and Fe³⁺ ions and is sometimesformulated as FeO.Fe₂O₃. It exhibits permanent magnetism and isferrimagnetic, although sometimes described as ferromagnetic. Itsparticle size and shape can be varied by the method of production. Fe₃O₄has a cubic inverse spinel structure which consists of a cubic closepacked array of oxide ions where all of the Fe²⁺ ions occupy half of theoctahedral sites and the Fe³⁺ are split evenly across the remainingoctahedral sites and the tetrahedral sites. Both FeO and γ-Fe₂O₃ have asimilar cubic close packed array of oxide ions and this accounts for theinterchangability between the three compounds on oxidation and reductionas these reactions entail a relatively small change to the overallstructure. Fe₃O₄ samples can be non-stoichiometric. In a preferredembodiment, the iron oxide nanoparticle core is substantially magnetite,Fe₃O₄.

Due to its four unpaired electrons in the 3d shell, an iron atom has astrong magnetic moment. Fe²⁺ ions also have four unpaired electrons inthe 3d shell and Fe³⁺ ions have five unpaired electrons in the 3d shell.Thus, when crystals are formed from iron atoms or Fe²⁺ and Fe³⁺ ionsthey can be ferromagnetic, antiferromagnetic or ferrimagnetic states.The ferrimagnetism of Fe₃O₄ arises because the electron spins of theFe^(II) and Fe^(III) ions in the octahedral sites are coupled and thespins of the Fe^(III) ions in the tetrahedral sites are coupled butanti-parallel to the former. The net effect is that the magneticcontributions of both sets are not balanced and there is permanentmagnetism.

In the paramagnetic state, the individual atomic magnetic moments arerandomly oriented, and the substance has a zero net magnetic moment ifthere is no magnetic field. These materials have a relative magneticpermeability greater than one and are attracted to magnetic fields. Themagnetic moment drops to zero when the applied field is removed.However, in a ferromagnetic material, all the atomic moments are alignedeven without an external field. A ferrimagnetic material is similar to aferromagnet but has two different types of atoms with opposing magneticmoments. The material has a magnetic moment because the opposing momentshave different strengths. If they have the same magnitude, the crystalis antiferromagnetic and possesses no net magnetic moment.Superparamagnetism is a form of magnetism, which appears in smallferrimagnetic or ferromagnetic nanoparticles. In sufficiently smallnanoparticles, magnetization can randomly flip direction under theinfluence of temperature. In a preferred embodiment, the iron oxidenanoparticle core is superparamagnetic, paramagnetic, ferromagnetic,antiferromagnetic and/or ferrimagnetic, more preferably the iron oxidein the iron oxide nanoparticle core possesses permanent magnetism andcomprises magnetite (Fe₃O₄) and/or its oxidized form maghemite(γ-Fe₂O₃), most preferably the iron oxide in the iron oxide nanoparticlecore possess permanent magnetism and is magnetite (Fe₃O₄).

The term “iron oxide nanoparticle core” as used herein refers to an ironoxide rich material (i.e. greater than 60%, preferably greater than 70%,preferably greater than 80%, more preferably greater than 90%, morepreferably greater than greater than 95%) onto which a single or aplurality of bis(diarylphosphinomethyl) dopamine based ligands areanchored to form a functionalized nanomaterial. In a preferredembodiment the iron oxide nanoparticle core is a maghemite (γ-Fe₂O₃)rich material (i.e. greater than 40%, preferably greater than 50%,preferably greater than 60%, preferably greater than 70%, preferablygreater than 80%, more preferably greater than 90%, more preferablygreater than greater than 95% maghemite). In a most preferred embodimentthe iron oxide nanoparticle core is a magnetite (Fe₃O₄) rich material(i.e. greater than 60%, preferably greater than 70%, preferably greaterthan 80%, more preferably greater than 90%, more preferably greater thangreater than 95% magnetite).

In a most preferred embodiment, the iron oxide nanoparticle core of thefunctionalized nanomaterial is magnetite (Fe₃O₄).

In addition to iron oxide, it is envisaged that the present disclosuremay be adapted to incorporate other metal oxide nanoparticles as a partof the functionalized nanomaterial. Exemplary metal oxides need only begenerally of low cost and preferably (or optionally) magnetic. Examplesof other metal oxides include, but are not limited to, oxides ofaluminum, zinc, copper, nickel, magenesium, zirconium, titanium,vanadium, rhodium, rhenium, silicon, molybdenum, thorium, chromium,manganese, cerium, silver, lead, cadmium, calcium, antimony, tin,bismuth, cobalt, tungsten and alloys or mixtures thereof.

In addition to iron oxide and/or iron, various non-ferrous materials(i.e. metals and non-metals) may be present in the iron oxidenanoparticle core including, but not limited to, aluminum, cobalt,copper, lead, nickel, tin, titanium, zinc, bronze, gold, silver,platinum, palladium, metal oxides thereof, metal sulfides thereof,calcium oxide, magnesium oxide, magnesite, dolomite, aluminum oxide,manganese oxide, silica, sulfur, phosphorous and combinations thereof.The total weight percent of these non-ferrous materials relative to thetotal weight of the iron oxide nanoparticle core is preferably no morethan 30%, preferably no more than 20%, preferably no more than 15%,preferably no more than 10%, preferably no more than 5%, preferably nomore than 4%, preferably no more than 3%, preferably no more than 2%,preferably no more than 1%, preferably no more than 0.5%.

The functionalized nanomaterials of the present disclosure also includea bis(phosphinomethyl) and/or bis(diarylphosphinomethyl) dopamine basedligand anchored to the surface of the iron oxide nanoparticle core byphenolic hydroxide groups to form a bis(phosphinomethyl) and/orbis(diarylphosphinomethyl) dopamine based ligand layer, and wherein thebisphosphine groups of the bis(phosphinomethyl) and/orbis(diarylphosphinomethyl) dopamine based ligand chelate a catalyticmetal or metal compound. As used herein, the terms “bis(phosphinomethyl)dopamine ligand” and “bis(phosphinomethyl) dopamine based ligand” and“bis(diarylphosphinomethyl) dopamine ligand and“bis(diarylphosphinomethyl) dopamine based ligand” are usedinterchangeably and may refer to all the dopamine ligands and dopaminederivative ligands described herein. The iron oxide nanoparticle corewith a bis(phosphinomethyl) and/or bis(diarylphosphinomethyl) dopaminebased ligand layer anchored to it is referred to herein as a“functionalized nanomaterial”.

In a most preferred embodiment, the bis(phosphinomethyl) dopamine basedligand is bis(diarylphosphinomethyl dopamine based ligand, mostpreferably the bis(phosphinomethyl) dopamine based ligand isbis(diphenylphosphinomethyl) dopamine.

Chemically, a dopamine molecule (FIG. 2, compound VI shows the HCl salt)consists of a catechol structure (a benzene ring with two hydroxyl sidegroups) with one amine group attached. As such, dopamine is the simplestpossible catecholamine, a family that also includes theneurotransmitters norepinephrine and epinephrine, additionally thepresence of the benzene ring with an attached amine group makes it aphenethylamine. Phenethylamine is a primary amine, the amino group beingattached to a benzene ring through a two-carbon or ethyl group. As usedherein, the “bis(phosphinomethyl) dopamine based ligand” and/or“bis(diarylphosphinomethyl) dopamine based ligand” refers to aphenethylamine derivative with at least one, preferably two or morephenolic hydroxide groups, and a tertiary amine with one sidechain ofthe formula —CH₂PR₁R₂ and another sidechain of the formula —CH₂PR₃R₄,preferably one sidechain of the formula —CH₂PAr₁Ar₂ and anothersidechain of the formula —CH₂PAr₃Ar₄, wherein Ar denotes an optionallysubstituted aryl group. The generic structure is shown (structure I):

As used herein, the term “aryl” unless otherwise specified refers tofunctional groups or substituents derived from an aromatic ringincluding, but not limited to, phenyl, biphenyl, naphthyl, thienyl, andindolyl and other heteroaryls. As used herein, the term optionallyincludes both substituted and unsubstituted moieties. Exemplary moietieswith which the aryl group can be substituted may be selected from thegroup including, but not limited to hydroxyl, halogen, amino,alkylamino, arylamino, alkoxy, aryloxy, nitro, cyano, sulfonic acid,sulfate, phosphonic acid, phosphate, or phosphonate or mixtures thereof.The substituted moiety may be either protected or unprotected asnecessary, and as known to those skilled in the art.

In a preferred embodiment, the benzene group of thebis(diarylphosphinomethyl) dopamine based ligand comprises 1-5 phenolichydroxide groups, preferably 2-4, preferably 2-3 or 2 as depicted instructure I. The phenolic hydroxide groups may be located ortho, para,or meta to the ethyl amine and mixtures thereof, preferably meta and/orpara. In addition to the phenolic hydroxide(s), the benzene ring may bemodified at any positions with groups for R₅-R₇ that may include, butare not limited to halogen groups, C₁-C₁₀ alkyl chains, alkoxyl groups,nitro groups, amino groups, mixtures thereof and the like.

In a preferred embodiment, the R₁, R₂, R₃ and R₄ groups of thebis(phosphinomethyl) dopamine based ligand are all the same, preferablyaryl, most preferably phenyl. In another embodiment three of the fourmay be the same, in another embodiment two of the four may be the same,preferably on the same side chain, and in another embodiment R₁, R₂, R₃and R₄ may all be different. The R₁-R₄ groups may include, but are notlimited to, straight C₁-C₁₀ alkyl chains (i.e. methyl, ethyl), branchedC₁-C₁₀ alkyl chains (i.e isopropyl), unsubstituted phenyl groups (Ph),and substituted phenyl groups.

In another embodiment, the tertiary amine of the bis(phosphinomethyl)dopamine based ligand may have sidechains of the formula (CH₂)_(x)PR₁R₂and (CH₂)_(y)PR₃R₄ and/or (CH₂)_(x)PAr₁Ar₂ and (CH₂)_(y)PAr₃Ar₄ where xand y may be the same or x and y may be different and x and y may havevalues in the range of 1-10, preferably 1-8, preferably 1-6, preferably1-5, preferably 1-4, preferably 1-3, preferably 1-2 or 1. In anotherembodiment, the tertiary amine is attached to the benzene ring through a1-10 carbon group rather than a generic 2 carbon or ethyl group,preferably 2-8, preferably 2-6, preferably a 2-4 carbon group which canbe modified with R₈-R₁₁ groups including, but not limited to halogengroups, alcohol groups, ester groups, amine groups, carbonyl groups andamide groups along the carbon chain. In another embodiment, the benzenering may be any appropriately sized aromatic hydrocarbon or heterocyclering system.

In a most preferred embodiment, the bis(phosphinomethyl) dopamine basedligand is a bis(diarylphosphinomethyl) dopamine based ligand. In a mostpreferred embodiment, the bis(diarylphosphinomethyl) dopamine basedligand is bis(diphenylphosphinomethyl) dopamine. The phenethylamine hastwo phenolic hydroxide groups located meta and para to the ethyl amineand R₁=R₂=R₃=R₄=Ph and R₅-R₁₁=H. In an alternative embodiment, theligand layer comprises bis(phosphinomethyl) norepinephrine basedligands.

The molecular structure of the bis(phosphinomethyl) and/orbis(diarylphosphinomethyl) dopamine based ligand features at least onephenolic hydroxide, preferably two, in a single molecule. In oneembodiment, these phenolic hydroxide groups are an anchor group thatbinds the iron oxide nanoparticle core. In one embodiment, the phenolichydroxide groups covalently bind the Fe²⁺ and/or Fe³⁺ ions comprisingthe iron oxide nanoparticle core, preferably two phenolic hydroxidegroups covalently bind. In one embodiment, it is envisaged that allphenolic hydroxide groups of the bis(diarylphosphinomethyl) dopaminebased ligand bind the iron oxide nanoparticle core. In anotherembodiment one or more of the phenolic hydroxide groups of thebis(diarylphosphinomethyl) dopamine based ligand may not bind the ironoxide nanoparticle core and may be located on the outer surface or becovalently modified.

In a preferred embodiment, the bisphosphine groups of thebis(diarylphosphinomethyl) dopamine based ligand of the functionalizednanomaterial are oriented to chelate a catalytic metal. Chelationdescribes a particular way that ions and molecules bind metal ions.Chelation involves the formation or presence of two or more separatecoordinate bonds between a polydentate (multiple bonded) ligand and asingle central atom. In a preferred embodiment, the catalytic metal isat least one selected from the group consisting of nickel, platinum,palladium, rhodium, iron, gold, silver, ruthenium and iridium.

Nanoparticles are particles between 1 and 100 nm (10² and 10⁷ atoms) insize. A particle is defined as a small object that behaves as a wholeunit with respect to its transport and properties. The exceptionallyhigh surface area to volume ratio of nanoparticles may cause thenanoparticles to exhibit significantly different or even novelproperties from those observed in individual atoms/molecules, fineparticles and/or bulk materials. Nanoparticles can be classifiedaccording to their dimensions. Three-dimensional nanoparticles have alldimensions of less than 100 nm, and generally encompass isodimensionalnanoparticles. Examples of three dimensional nanoparticles include, butare not limited to, nanoparticles, nanospheres, nanogranules andnanobeads. Two-dimensional nanoparticles have two dimensions of lessthan 100 nm, generally including diameter. Examples of two-dimensionalnanoparticles include, but are not limited to, nanotubes, nanofibers andnanowhiskers. One-dimensional nanoparticles have one dimension of lessthan 100 nm, generally thickness. Examples of one-dimensionalnanoparticles include, but are not limited to, nanosheets,nanoplatelets, nanolaminas and nanoshells. The iron oxide nanoparticlecore and the functionalized nanomaterial of the present disclosure arepreferably three-dimensional nanoparticles, but may also beone-dimensional, two-dimensional, three-dimensional or mixtures thereof.

In the present disclosure, the iron oxide nanoparticle core is coveredwith a thin coating or bis(diarylphosphinomethyl) dopamine based ligandlayer which may be continuous or discontinuous. Therefore, the generalshape and size of the iron oxide nanoparticle core may dictate the shapeand size of the functionalized nanomaterial described herein.Nanoparticles are named for the real-world shapes that they appear torepresent. These morphologies sometimes arise spontaneously as an effectof the synthesis or from the innate crystallographic growth patterns ofthe materials themselves. Some of these morphologies may serve apurpose, such as bridging an electrical junction.

In a preferred embodiment, the iron oxide nanoparticle cores andfunctionalized nanomaterials of the present disclosure are in the formof a nanoparticle, which is spherical or substantially spherical (e.g.oval, oblong, etc.) in shape. Alternatively, it is envisaged that theiron oxide nanoparticles may have a more polygonal shape and may begenerally cubic or rectangular. However, the iron oxide nanoparticlesdisclosed herein may have various shapes other than spheres and may beof any shape that provides desired synthetic activity and/or desiredproperties in the resulting functionalized nanomaterial. In a preferredembodiment, the iron oxide nanoparticle cores and the functionalizednanomaterial have a spherical morphology.

In one embodiment, the iron oxide nanoparticle core and thefunctionalized nanomaterial of the present disclosure are envisaged tobe synthesized and formed into a variety of morphologies and formsincluding, but not limited to, nanoparticles, nanosheets, nanoplatelets,nanocrystals, nanospheres, nanorectangles, nanotriangles, nanopentagons,nanohexagons, nanoprisms, nanodisks, nanocubes, nanowires, nanofibers,nanoribbons, nanorods, nanotubes, nanocylinders, nanogranules,nanowhiskers, nanoflakes, nanofoils, nanopowders, nanoboxes, nanostars,tetrapods, nanobelts, nanaourchins, nanofloweres, etc. and mixturesthereof.

In one embodiment, the iron oxide nanoparticle core and thefunctionalized nanomaterial have uniform shape. Alternatively, the shapemay be non-uniform. As used herein, the term “uniform” refers to anaverage consistent shape that differs by no more than 10%, by no morethan 5%, by no more than 4%, by no more than 3%, by no more than 2%, byno more than 1% of the distribution of iron oxide nanoparticles having adifferent shape. As used herein, the term “non-uniform” refers to anaverage consistent shape that differs by more than 10% of thedistribution of iron oxide nanoparticles having a different shape. Inone embodiment, the shape is uniform and at least 90% of thefunctionalized nanomaterial are spherical or substantially circular, andless than 10% are polygonal or substantially square. In anotherembodiment, the shape is non-uniform and less than 90% of thefunctionalized nanomaterial are spherical or substantially circular, andgreater than 10% are polygonal or substantially square.

Nanoparticle characterization is necessary to establish understandingand control of nanoparticle synthesis, assembly and application. In oneembodiment, the nanoparticles and functionalized nanomaterial arecharacterized by at least one technique selected from the groupconsisting of electron microscopy (TEM, SEM, FESEM), powder X-raydiffraction (MUD), thermogravimetric analysis (TGA) and Fouriertransform infrared spectroscopy (FT-IR). In another embodiment, it isenvisioned that characterization is done using a variety of othertechniques. Exemplary techniques include, but are not limited to,ultraviolet-visible spectroscopy (UV-Vis), atomic force microscopy(AFM), dynamic light scattering (DLS), X-ray photoelectron spectroscopy(XPS), X-ray fluorescence (XRF), energy-dispersive X-ray spectroscopy(EDX), matrix-assisted laser desorption/ionization time-of-flight massspectrometry (MALDI-TOF), Raman spectroscopy, Rutherford backscatteringspectrometry (RBS), dual polarization interferometry, and nuclearmagnetic resonance (NMR) or mixtures thereof.

The size of the iron oxide nanoparticle core may also dictate the sizeof the functionalized nanomaterial described herein. For spherical orsubstantially spherical iron oxide nanoparticles, average particle sizerefers to the average longest linear diameter of the iron oxidenanoparticles. For non-spherical iron oxide nanoparticles, such ascubes, squares and/or rectangles the average particle size may refer tothe longest linear dimension and any of the length, width or height. Inone embodiment, the functionalized nanomaterial of the presentdisclosure are monodispersed with an average particle size of 1-20 nm,preferably 2-15 nm, preferably 3-10 nm, preferably 4-8 nm, or mostpreferably 5-7 nm. In one embodiment, the functionalized nanomaterial ofthe present disclosure are monodispersed with an average particle sizeof greater than 20 nm, preferably 20-1000 nm, preferably 20-500 nm,preferably 20-250 nm, preferably 20-200 nm, preferably 20-150 nm,preferably 20-100 nm, preferably 20-75 nm, preferably 20-50 nm,preferably 20-40 nm, preferably 20-30 nm. The size may vary from theseranges and still provide acceptable functionalized nanomaterial.

In a preferred embodiment, the iron oxide nanoparticle core andfunctionalized nanomaterial of the present disclosure are monodisperse,having a coefficient of variation or relative standard deviation,expressed as a percentage and defined as the ratio of the particle sizestandard deviation (σ) to the particle size mean (μ) multiplied by 100of less than 25%, preferably less than 20%, preferably less than 15%,preferably, less than 12%, preferably less than 10%, preferably lessthan 8%, preferably less than 6%, preferably less than 5%, preferablyless than 4%, preferably less than 3%, preferably less than 2%. In apreferred embodiment, the iron oxide nanoparticle core andfunctionalized nanomaterial of the present disclosure are monodispersehaving a particle size distribution ranging from 80% of the averageparticle size to 120% of the average particle size, preferably 90-110%,preferably 95-105% of the average particle size.

In one embodiment, the bis(diarylphosphinomethyl) dopamine based ligandlayer may “substantially cover” the surface of the iron oxidenanoparticle core, whereby the percent surface area coverage of thesurface being covered is at least 70%, at least 75%, at least 85%, atleast 90%, at least 95%, at least 96%, at least 97%, at least 98%, atleast 99%. In another embodiment, the bis(diarylphosphinomethyl)dopamine based ligand layer may “incompletely cover”, or only coverportions of the surface of the iron oxide nanoparticle core, whereby thepercent surface area coverage of the surface being covered is less than70%, less than 65%, less than 60%, less than 55%, less than 50%, lessthan 45%, less than 40%, less than 35%, less than 30%, less than 25%,less than 20%, less than 15%, or 10%.

The bis(diarylphosphinomethyl) dopamine based ligand layer may refer toone material (i.e. bis(methyldiphenylphosphino) dopamine and/orderivatives thereof) that covers the surface of the iron oxidenanoparticle core being functionalized, or alternatively thebis(diarylphosphinomethyl) dopamine based ligand layer may refer to amixture of interspersed individual materials includingbis(methyldiphenylphosphino) dopamine and one or more additionalbis(phosphinomethyl) and/or bis(diarylphosphinomethyl) dopamine basedligands or other ligands or sequential applications of individualmaterials including bis(methyldiphenylphosphino) dopamine and one ormore additional bis(phosphinomethyl) and/or bis(diarylphosphinomethyl)dopamine based ligands or other ligands. With sequential applications ofindividual materials, it may be possible to form distinct layers andthese distinct layers may have a defined interface. Thebis(phosphinomethyl) dopamine based ligand layer may also refer to asingle application of a material or a plurality of applications of thesame material and may comprise a monolayer, a bilayer, a trilayer and/ora multilayer.

In a preferred embodiment, the bis(diarylphosphinomethyl) dopamine basedligand layer substantially covers the iron oxide nanoparticle core,where the bis(diarylphosphinomethyl) dopamine based ligand coversgreater than 70%, preferably greater than 75%, preferably greater than80%, preferably greater than 85%, preferably greater than 90%,preferably greater than 95% of the surface of the iron oxidenanoparticle core. Alternatively, the bis(diarylphosphinomethyl)dopamine based ligand layer may only cover a portion of the surface ofiron oxide nanoparticle core (i.e. incompletely cover), where thebis(diarylphosphinomethyl) dopamine based ligand layer covers less than70%, less than 65%, less than 60%, less than 55%, less than 50%, lessthan 40%, less than 30%, less than 25%, less than 20%, less than 15%,less than 10% of the surface of the iron oxide nanoparticle core and thebis(diarylphosphinomethyl) dopamine based ligand layer may still providesufficient functionalized nanomaterial for chelation of a catalyticmetal.

In a preferred embodiment, the functionalized nanomaterial of thepresent disclosure has 0.2-1.0 mmol of phosphine per gram offunctionalized nanomaterial, preferably 0.25-0.9 mmol per gram,preferably 0.3-0.8 mmol per gram, preferably 0.35-0.7 mmol per gram,preferably 0.4-0.6 mmol per gram, or 0.5 mmol of phosphine per gram offunctionalized nanomaterial. It is envisaged that functionalizednanomaterials having phosphine loadings outside of these ranges may alsofunction as intended.

In one embodiment, the functionalized nanomaterial of the presentdisclosure has a weight percentage of the bis(diarylphosphinomethyl)dopamine ligand layer ranging from 0.05-5.0%, preferably 0.1-2.5%,preferably 0.2-2.0%, preferably 0.25-1.5%, preferably 0.25-1.0% based onthe total weight of bis(diarylphosphinomethyl) dopamine ligands bondedto the iron oxide nanoparticle core relative to the total weight of thefunctionalized nanomaterial. These ranges describe thebis(diarylphosphinomethyl) dopamine ligand when not bound to a catalyticmetal, and it is envisaged that these ranges may change upon chelationto a catalytic metal, depending on the amount and type of catalyticmetal.

In one embodiment, the average thickness of thebis(diarylphosphinomethyl) dopamine based ligand layer is less than 5nm, preferably less than 4 nm, preferably less than 3.5 nm, preferablyless than 3 nm, preferably less than 2.5 nm, preferably less than 2 nm,preferably less than 1.5 nm, preferably less than 1 nm. In a preferredembodiment, the bis(diarylphosphinomethyl) dopamine based ligand layeris of uniform thickness. Alternatively, the bis(diarylphosphinomethyl)dopamine based ligand layer may be of non-uniform thickness. The term“uniform thickness” refers to an average layer thickness that differs byno more than 5%, by no more than 4%, by no more than 3%, by no more than2%, by no more than 1% at any given location on the surface of the ironoxide nanoparticle core. The term “non-uniform thickness” refers to anaverage layer thickness that differs by more than 5% at any givenlocation on the surface of the iron oxide nanoparticle core.

The thermal stability as well as the strong attachment of thebis(diarylphosphinomethyl) dopamine based ligand to the iron oxidenanoparticle core are important for its functionality. In a preferredembodiment, the functionalized nanomaterial of the present disclosureloses less than 1% of its total weight when heated to a temperature of200° C. Additionally, this weight loss may be entirely due to the lossof water molecules and not signify any loss of boundbis(diarylphosphinomethyl) dopamine based ligand. In a preferredembodiment, the functionalized nanomaterial of the present disclosureloses no more than 10% of its total weight, preferably no more than 7%,preferably no more than 5%, preferably no more than 4%, preferably nomore than 3%, preferably no more than 2% of its total weight afterheating at temperatures up to 200-500° C. for one hour. This weight lossmay be attributed to the elimination of bis(diarylphosphinomethyl)dopamine based ligands in one or several steps. In a preferredembodiment, the functionalized nanomaterial loses no more than 75%,preferably no more than 50%, preferably no more than 40%, preferably nomore than 30%, preferably no more than 25%, preferably no more than 20%,preferably no more than 15%, preferably no more than 10%, preferably nomore than 5% of its bis(diarylphosphinomethyl) dopamine based ligandsfrom the surface at temperatures of up to 500° C.

According to a second aspect, the present disclosure relates to aprocess for producing the functionalized nanomaterial of the presentdisclosure in any of its embodiments. The preparation method of the ironoxide nanomaterial has a large effect on shape, size distribution, andsurface chemistry of the particles. It also determines the distributionand types of structural defects or impurities in the particles. All ofthese factors can affect the behavior, especially magnetic behavior, ofthe iron oxide nanoparticles.

In a preferred embodiment the iron oxide nanoparticle core issynthesized by coprecipitation techniques, i.e. by precipitating an ironsalt under alkaline conditions. This method can be further divided intotwo types. The preferred type comprises ageing stoichiometric mixturesof ferrous and ferric hydroxides in aqueous media yielding sphericalmagnetite particles homogeneous in size. In the preferred type, thefollowing chemical reaction occurs (formula I):2Fe³⁺+Fe²⁺+80H⁻→Fe₃O₄+4H₂O  (I):The size and shape of the nanoparticles can be controlled by adjustingpH, ionic strength, temperature, nature of the salts (i.e. perchlorates,chlorides, sulfates and nitrates) and/or the Fe (II)/Fe (III)concentration ratio. Advantageous conditions for this reaction are a pHin the range of 8-14, preferably 8.25-12, preferably 8.5-10, preferably8.75-9.75, most preferably 9. In a preferred embodiment, the pH ismaintained by ammonium hydroxide but a variety of bases are envisaged,including hydroxide, carbonates and bicarbonates of alkali metals oralkaline earth metals. Advantageous conditions for this reaction are aratio of 2:1 for Fe³⁺ to Fe²⁺. Advantageous conditions for this reactionare a non-oxidizing environment. Being highly susceptible to oxidation,magnetite (Fe₃O₄) is transformed to maghemite (γ-Fe₂O₃) in the presenceof oxygen but the following chemical reaction (formula 2):2Fe₃O₄+O₂→2γFe₂O₃  (II):

In another embodiment, the iron oxide nanoparticle core may be envisagedto be synthesized by the other type of coprecipitation technique. Inthis method, ferrous hydroxide suspensions are partially oxidized withdifferent oxidizing agents. For example, spherical magnetite particlesof narrow size distribution can be obtained from a Fe(II) salt, a baseand a mild oxidant (i.e. nitrate ions).

In a preferred embodiment, the source of iron (III) is iron (III)chloride (FeCl₃). In another embodiment, it is envisaged that thepresent disclosure may be adapted to incorporate other sources of iron(III) in addition to iron (III) chloride including, but not limited to,iron (III) acetylacetonate, iron (III) nitrate, iron (III) tartrate,iron (III) sulfate, iron (III) trifluoromethanesulfonate, iron (III)bromide, iron (III) perchlorate, iron (III) phosphate, iron (III)oxalate, iron (III) fluoride, iron (III) p-toluenesulfonate and hydratesand/or mixtures thereof.

In a preferred embodiment, the source of iron (II) is iron (II) chloride(FeCl₂). In another embodiment, it is envisaged that the presentdisclosure may be adapted to incorporate other source of iron (II) inaddition to iron (II) chloride including, but not limited to, iron (II)iodide, iron (II) sulfate, iron (II) acetate, iron (II) acetylacetonate,iron (II) oxalate, iron (II) bromide, iron (II) lactate, iron (II)molybdate, iron (II) perchlorate, iron (II) gluconate, iron (II)tetrafluoroborate, iron (II) fluoride, iron (II) fumarate, iron (II)trifluoromethanesulfonate, iron (II) ethylenediammonium sulfate andhydrates and/or mixtures thereof.

In another embodiment, the iron oxide nanoparticle core may be envisagedto be synthesized by microemulsion techniques. A microemulsion is astable isotropic dispersion of 2 immiscible liquids consisting ofnanosized domains of one or both liquids in the other stabilized by aninterfacial film of surface-active molecules. Microemulsions may becategorized further as oil-in-water (o/w) or water-in-oil (w/o),depending on the dispersed and continuous phases. Water-in-oil is morepopular for synthesizing many kinds of nanoparticles. The water and oilare mixed with an amphiphilic surfactant. The surfactant lowers thesurface tension between water and oil, making the solution transparent.The water nanodroplets act as nanoreactors for synthesizingnanoparticles. The shape of the water pool is spherical. The size of thenanoparticles will depend on the size of the water pool to a greatextent; thus, the size of the spherical nanoparticles can be tailoredand tuned by changing the size of the water pool.

In another embodiment, the iron oxide nanoparticle core may be envisagedto be synthesized by high temperature decomposition of organic precursortechniques. The decomposition of iron precursors in the presence of hotorganic surfactants results in samples with good size control, narrowsize distribution and good crystallinity; and the nanoparticles areeasily dispersed. Viable iron precursors include, but are not limitedto, Fe(Cup)₃, Fe(CO)₅, or Fe(acac)₃ in organic solvents with surfactantmolecules. A combination of xylenes and sodium dodecylbenzensulfonate asa surfactant are used to create nanoreactors for which well dispersediron (II) and iron (III) salts can react.

The process for forming the bis(diarylphosphinomethyl) dopamine basedligand involves preparing phosphinoalcohol, preferably phosphinemethanol, preferably diaryl phosphine methanol by the reaction ofparaformaldehyde and desired phosphine of the formula (HPR₁R₂ or HPR₃R₄and/or HPAr₁Ar₂ or HPAr₃Ar₄). In a preferred embodiment, the reaction isperformed in a dry non-polar solvent (i.e. toluene) and heated to50-200° C., preferably 80-150° C., preferably 90-140° C., preferably100-130° C., preferably 110-125° C. or 120° C. for 2-12 hours,preferably 2-10 hours, preferably 2-8 hours, preferably 2-6 hours or 4hours. In one embodiment, what begins as a turbid solution should becomeclear as the reaction proceeds. In the third step, a dopamine basedsalt, preferably dopamine hydrochloride, is added in situ to the abovereaction mixture without isolation of the phosphinoalcohol and thereaction is heated at 50-200° C., preferably 80-150° C., preferably90-140° C., preferably 100-130° C., preferably 110-125° C. or 120° C.for 2-48 hours, preferably 8-36 hours, preferably 12-36 hours,preferably 20-30 hours or 24 hours to form thebis(diarylphosphinomethyl) dopamine based ligand as a precipitatedsticky solid that after drying under vacuum is obtained as a creamcolored solid in a yield of over 50% from the phosphine, preferably over75%, preferably over 80%, preferably over 85%, preferably over 90%,preferably over 95%.

The functionalized nanomaterial is formed by mixing a solution orsuspension of the prepared iron oxide nanoparticle cores with a solutionor suspension of the prepared bis(diarylphosphinomethyl) dopamine basedligand. The reaction is carried out by sonication for up to 12 hours,preferably up to 10 hours, preferably up to 8 hours, preferably up to 6hours, preferably up to 4 hours, preferably up to 2 hours. Thefunctionalized nanomaterial may be obtained as a light black coloredpowder that is collected with the aid of a strong magnet after washingrepeatedly. In a preferred embodiment, the bis(diarylphosphinomethyl)dopamine based ligand is in an anhydrous polar protic solvent (i.e.short chain alcohols such as methanol, ethanol, n-propanol, isopropanol,n-butanol) and the iron oxide nanoparticles are in an anhydrousnon-polar solvent (i.e. chloroform).

According to a third aspect, the present disclosure relates to a methodfor the hydroformylation of an olefin to a corresponding aldehydeutilizing the functionalized nanomaterial of the present disclosure inany of their embodiments. The method includes mixing the functionalizednanomaterial of the present disclosure in any of their embodiments withthe olefin, adding a rhodium salt as a source of the catalytic metal andthen hydroformylating the olefin in the presence of carbon monoxide or acarbon monoxide surrogate.

Hydroformylation, also known as oxo synthesis or oxo process is animportant industrial process for the production of aldehydes fromalkenes. This chemical reaction entails the addition of a formyl group(CHO) and a hydrogen atom to a carbon-carbon double bond. It isimportant because the resulting aldehydes are easily converted into manysecondary products. For example, the resulting aldehydes arehydrogenated to alcohols that are converted to plasticizers ordetergents. Hydroformylation is also used in specialty chemicals,relevant to the organic synthesis of fragrances and natural products.The process typically entails treatment of an alkene with high pressures(between 10-100 atmospheres) of carbon monoxide and hydrogen attemperatures between 40 and 200° C. Transition metal catalysts arerequired.

The overall mechanism resembles that for homogeneous hydrogenation withadditional steps. The reaction begins with the generation of acoordinatively unsaturated metal hydrido carbonyl complex such asHCo(CO)₃ or HRh(CO)(PPh₃)₃. Such species bind alkenes, and the resultingcomplex undergoes a migratory insertion reaction to form an alkylcomplex. After the alky formation a second migratory insertion convertsthe alkyl into an acetyl ligand, this is when the alkyl carbon forms abond with the carbon of a carbonyl ligand. The vacant site on the metalis filled by two hydrogens, from the oxidative insertion of a hydrogenmolecule. One of these hydrides then takes part in a reductiveelimination to form the molecule of the aldehyde and the complex.

A key consideration of hydroformylation is the “normal” (linear) versus“iso” (branched) selectivity. For examples, the hydroformylation ofpropylene can afford two isomeric products, butyraldehyde orisobutyraldehyde. These isomers result from differing ways of insertingthe alkene into the metal-hydrogen bond. Although, both products areequally desirable, significant effort has been dedicated to a catalystthat favors the normal or linear isomer. One controlling factor issteric effects. When the hydrogen is transferred to the carbon bearingthe most hydrogen atoms (Markovnikov addition) the resulting alkyl grouphas a larger steric bulk close to the ligands of the metal. If theligands on the metal are bulky (i.e. tributyl phosphine or diphenylphosphine) then the steric effect is greater and the mixedcarbonyl-phospine complexes offer a greater selectivity toward thestraight chain linear products. Another controlling factor is electroniceffects. The more electron-rich the hydride complex is the lessproton-like the hydride is. Thus, as a result, the electronic effectsthat favor the Makovnikov addition to an alkene are less able to directthe hydride to the carbon atom bearing the most hydrogens already. Thus,as a result, as the metal center becomes more electron-rich, thecatalyst becomes more selective for the straight chain linear compounds.In one embodiment, the corresponding aldehyde of the present disclosurehas a linear (“normal”) aldehyde form and a branched (“iso”) aldehydeform and the ratio of the linear aldehyde form to branched aldehyde formis greater than or equal to 1, preferably greater than 1.05, preferablygreater than 1.10, preferably greater than 1.15, preferably greater than1.20, preferably greater than 1.3, preferably greater than 1.4,preferably greater than 1.5, preferably greater than 1.75, preferablygreater than 2. In another embodiment, it is envisaged that the currentmethod may be adapted to have a ratio of the linear aldehyde form tobranched aldehyde form of less than 1, preferably less than 0.95,preferably less than 0.9, preferably less than 0.85, preferably lessthan 0.8, preferably less than 0.75, preferably less than 0.5,preferably less than 0.25.

In another embodiment, the hydroformylation of prochiral alkenes createsnew stereocenters. Using chiral bis(phosphinomethyl) and/orbis(diarylphosphinomethyl) dopamine based ligands having chiralphosphine ligands, chiral dopamine based structures (e.g.norepinephrine) or both, the hydroformylation can be tailored to favorone enantiomer of the newly generated stereogenic center.

In a preferred embodiment, the percent conversion from the olefin to thecorresponding aldehyde is greater than 90%, preferably greater than 91%,preferably greater than 92%, preferably greater than 93%, preferablygreater than 94%, preferably greater than 95%, preferably greater than96%, preferably greater than 97%, preferably greater than 98%,preferably greater than 99%, preferably greater than 99.5%, preferablygreater than 99.9%. The percent conversion may vary from this range andstill provide acceptable functionalized nanomaterial having increasedselectivity for the linear aldehyde product versus the branched aldehydeproduct.

In one embodiment, the method for the hydroformylation of an olefin to acorresponding aldehyde utilizing the functionalized nanomaterial of thepresent disclosure in any of its embodiments further comprisesrecovering and reusing the functionalized nanomaterial in at least 2reaction iterations, preferably at least 3, preferably at least 4,preferably at least 5, preferably at least 6, preferably at least 8,preferably at least 10, preferably at least 15, preferably at least 20reaction iterations. The functionalized nanomaterial can be recoveredvia magnetic extraction and washed several times with a solvent such asdichloromethane to remove all materials present after each round ofcatalysis and then be recycled with an appropriate amount of rhodium. Ina preferred embodiment, there is less than a 10% loss in percentconversion from the olefin to the corresponding aldehyde between thefirst and second iteration, preferably less than 5%, preferably lessthan 4%, preferably less than 3%, preferably less than 2% loss inpercent conversion. In another embodiment, there is less than a 20% lossin percent conversion from the olefin to the corresponding aldehydebetween the first and third iteration, preferably less than 15%,preferably less than 10% in percent conversion. In another embodiment,there is less than a 35% loss in percent conversion from the olefin tothe corresponding aldehyde between the first and fourth iteration,preferably less than 30%, preferably less than 25%, preferably less than20% loss in percent conversion.

The performance of the hydroformylation can be controlled by adjustingconditions such as temperature, pressure, solvent and/or catalystloading. In a preferred embodiment, the hydroformylation is carried outat temperatures below 150° C., preferably below 125° C., preferablybelow 100° C., preferably below 90° C., preferably below 75° C.,preferably below 50° C., preferably below 30° C. or at room temperature.In a preferred embodiment, the carbon monoxide surrogate is syngas orsynthesis gas, a mixture comprising primarily hydrogen, carbon monoxideand often some carbon dioxide. In a preferred embodiment, thehydroformylation is carried out under less than 300 psi of pressure inthe presence of syngas, preferably less than 275 psi, preferably lessthan 250 psi, preferably less than 225 psi, preferably less than 200psi, preferably less than 150 psi of pressure in the presence of syngas.In a preferred embodiment, the hydroformylation is carried out inanhydrous solvent, preferably a non-polar solvent or a polar aproticsolvent. Exemplary non-polar solvents include, but are not limited totoluene, pentane, cyclopentane, hexane, cyclohexane, benzene, toluene,1,4-dioxane, chloroform, diethyl ether and dichloromethane. Exemplarypolar aprotic solvents include, but are not limited to, tetrahydrofuran(THF), ethyl acetate, acetone, dimethylformamide (DMF), acetonitrile(MeCN), dimethyl sulfoxide (DMSO), nitromethane and propylene carbonate.In a preferred embodiment, the hydroformylation is carried out using nomore than 50 mg of functionalized nanomaterial per 1.0 mmol of olefin,preferably no more than 45 mg, preferably no more than 40 mg, preferablyno more than 35 mg, preferably no more than 30 mg, preferably no morethan 25 mg, preferably no more than 20 mg of functionalized nanomaterialper 1.0 mmol of olefin. The conditions may vary from these ranges andstill provide acceptable conditions for performing the hydroformylationutilizing the functionalized nanomaterial of the present disclosure.

The general nature of the olefin substrate is not viewed as particularlylimiting to the hydroformylation described herein. In one embodiment,the olefin is a styrene. Styrene, also known as ethenylbenzene,vinylbenzene, and phenylethene, is an organic compound with the chemicalformula C₆H₅CHCH₂. The derivative of benzene is a colorless oily liquidthat evaporates easily. It is envisaged that the present disclosure maybe adapted to incorporate other styrene derivatives and the benzyl ringof styrene may be modified with a group R₁-R₅ which may include, but arenot limited to, an electron withdrawing group, an electron donatinggroup, halogen groups, C₁-C₁₀ alkyl chains, alkoxyl groups and the likeand mixtures thereof. Exemplary styrene derivatives include, but are notlimited to, styrene, 4-methyl styrene, 4-vinylanisole, 2-vinylanisole,3-vinylanisole, 4-chlorostyrene, 3-nitrostyrene, 4-trifluoromethylstyrene, 3-trifluoromethyl styrene, 2-trifluoromethyl styrene,4-[N-(methylaminoethyl)aminomethyl] styrene and mixtures thereof.

In a preferred embodiment, the rhodium salt and source of rhodiumcatalytic metal is rhodium (III) chloride, RhCl₃ of2,5-norbornadiene-rhodium (I) chloride dimer, [Rh(NBD)Cl]₂. In anotherembodiment, it is envisaged that the present disclosure may be adaptedto incorporate other sources of rhodium including, but not limited to,rhodium (III) nitrate, rhodium (III) acetylacetonate, rhodium (III)sulfate, ammonium hexachlororhodate (III), rhodium (III) oxide andhydrates and/or mixtures thereof. In another embodiment, it is envisagedthat the present disclosure may be adapted to incorporate other sourcesof rhodium including, but not limited to chloro (1,5-cyclooctadiene)rhodium (I) dimer, bicycle [2.2.1] hepta-2,5-diene rhodium (I) chloridedimer, (acetylacetonato) (norbornadiene) rhodium (I),hydroxyl(cyclooctadiene) rhodium (I) dimer, chloro bis(cyclooctene)rhodium (I) dimer, methoxy (cyclooctadiene) rhodium (I) dimer, hydroxy[—(S)-BINAP] rhodium (I) dimer and hydrates and/or mixtures thereof.Furthermore, it is envisioned that the hydroformylation described hereinmay be adapted to incorporate alternative catalytic metals to rhodium,such as cobalt.

According to a fourth aspect, the present disclosure relates to acatalyst composition comprising the functionalized nanomaterial of thepresent disclosure in any of their embodiments and a catalytic metal,wherein the functionalized nanomaterial chelates the catalytic metal. Ina preferred embodiment, the catalytic metal is at least one selectedfrom the group consisting of nickel, platinum, palladium, rhodium, iron,gold, silver, ruthenium and iridium. The catalyst composition isenvisioned to possess a wide range of catalytic applications from itscoordination mode with different metals.

Heterogeneous catalysts refer to catalysts where the phase of thecatalyst differs from that of the reactants. Homogeneous catalysts referto catalysts where the phase of the catalyst is the same as that of thereactants. In terms of the present disclosure, the catalyst compositionmay function as a heterogeneous catalyst, a homogeneous catalyst, orhave components that function and have properties of both aheterogeneous catalyst and a homogeneous catalyst.

In a preferred embodiment, the catalyst composition is employed in atleast one chemical transformation selected from the group including, butnot limited to, hydrogenations, palladium-catalyzed coupling reactionsand selective oxidations.

In one embodiment, the catalytic composition may comprise thefunctionalized nanomaterial chelating rhodium and be employed in achemical transformation such as a hydrogenation. In one embodiment, thehydrogenation may be an asymmetric hydrogentation. Exemplary rhodiumcatalyzed hydrogenations include, but are not limited to, thehydrogenation of alkenes, the hydrogenation of alkynes, thehydrogenation of aromatic cyclic arenes, the hydrogenation of nitriles,and the hydrogenation of pyridines and N-heterocycles.

In one embodiment, the catalytic composition may comprise thefunctionalized nanomaterial chelating palladium and be employed in achemical transformation such as palladium-catalyzed coupling reactions.Exemplary palladium catalyzed coupling reactions include, but are notlimited to, Negishi couplings (between an organohalide and an organozinccompound), Heck reactions (between alkenes and aryl halides), Suzukireactions (between aryl halides and boronic acids), Stille reactions(between organohalides and organotin compounds), Hiyama couplings(between organhalides and organosilicon compounds), Sonagashiracouplings (between aryl halides and alkynes, with copper (I) iodide as aco-catalyst), the Buchwald-Hartwig amination of an aryl halide with anamine, the Kumada coupling of grignards and aryl or vinyl halides, andthe Heck-Matsuda reaction of an arenediazonium salt and an alkene.

In one embodiment, the catalytic composition may comprise thefunctionalized nanomaterial chelating palladium and/or platinum and beemployed in a chemical transformation such as the selective oxidation ofalcohols and aldehydes or allylic alkylations. In one embodiment, thecatalytic composition may comprise the functionalized nanomaterialchelating palladium or ruthenium and be employed in a chemicaltransformation such as Suzuki reactions, Suzuki-Miyuara couplings,Miyuara-Heck couplings, Mizoroiki-Heck couplings, Heck arylations andvinylations, Tsuji-Trost reactions (additions to π-allyls), olefinmetathesis and/or aromatic carbon-heteroatom bond forming reactions.

The examples below are intended to further illustrate protocols forpreparing and characterizing the functionalized nanomaterial of thepresent disclosure. Further, they are intended to illustrate assessingthe properties of these nanomaterials. They are not intended to limitthe scope of the claims.

Example 1 Chemicals

All reactions were carried out under argon atmosphere using standardSchlenk technique. Chemicals were all purchased from Sigma-AldrichCompany and were utilized directly as received without furtherpurification unless otherwise noted. Deionized (DI) water was obtainedfrom a water purification system and used wherever needed.

Example 2 Synthesis of Magnetic Nanoparticles (MNPs)

Magnetite (Fe₃O₄) nanoparticles in the range of 5-7 nm were synthesized(FIG. 1) according to the procedure reported in the literature [J. HeeYang, B. Ramaraj and K. R. Yoon, Journal of Alloys and Compounds 2014,583, 128—incorporated herein by reference in its entirety]. The magneticnanoparticles were prepared by co-precipitation techniques with thereaction of a 1:2 molar mixture of Fe (II) and Fe (III) precursors. Themedium of the reaction was made alkaline using concentrated ammoniumhydroxide and the pH was kept constant at 9 for 4 hours. The blackcolored solid materials were collected using a strong magnet afterrepeated washing with water to remove unreacted iron precursors (FIG.1).

Briefly, 2 grams of hydrated FeCl₂ (10 mmol) and 8.08 g of FeCl₃ (20mmol) were dissolved in 200 mL of deionized water under argon at 90° C.with vigorous stirring. Concentrated NH₄OH was slowly added until thesolution attained a pH of 9, attended by precipitation. The mixture wasallowed to stand for 4 h. The precipitate (black) was washed severaltimes with deionized (DI) water and dried.

Example 3 Synthesis of Bis(Methyldiphenylphosphino) Dopamine (Bpd)Ligand

Dopamine was functionalized by a double phosphinomethylation step onprimary amine via reaction of dopamine hydrochloride anddiphenylphosphinomethanol (FIG. 2). The first step of this reaction wasto prepare phosphinoalcohol. Diphenylphosphine was allowed to react withparaformaldehyde in dry toluene under heating at 120° C. for 4 hours andthe turbid solution became clear. The dopamine was phosphinylated usinga straight forward reaction with quantitative yield [I. Angurell, C.-O.Turrin, R. Laurent, V. Maraval, P. Servin, O. Rossell, M. Seco, A.-M.Caminade and J.-P. Majora, Journal of Organometallic Chemistry 2007,692, 1928; and P. Servin, R. Laurent, A. Romerosa, M. Peruzzini, J.-P.Majoral, and A.-M. Caminade, Organometallics 2008, 27, 2066—eachincorporated herein by reference in its entirety]. In this reaction,equimolar amounts of dopamine hydrochloride were added in situ into thereaction system and it was heated to reflux at 120° C. for another 24hours and subsequently precipitated as a sticky solid and after dryingunder vacuum was obtained as a cream color solid in 90% yield.

Briefly, 1.75 mL of diphenylphosphine (10 mmol) was added to thesuspension of 2.9 g paraformaldehyde (9.5 mmol) in 10 mL anhydroustoluene under argon. The mixture was stirred for 4 h at 120° C. toobtain a clear solution. To this clear solution 0.76 g of dopaminehydrochloride (4 mmol) was added and the solution was refluxed for 24 hat 120° C. This resulted in a creamy suspension from which solidbis(methyldiphenylphosphino) dopamine ligand was obtained by filtrationand subsequent washing, first with toluene and then with DI water.³¹P{H} NMR (200 MHz, in DMSO-d₆): δ-28.71 (s, PPh₂) ppm. ¹H NMR (500MHz, DMSO-d₆): δ 2.49 (t, 2H, NCH₂CH₂), 3.69 (t, 2H, NCH₂CH₂), 4.14 (brd, 4H, CH₂P), 6.47 (br s, 2H, OH), 6.55 (2H, CH), 6.74 (br s, 1H, CH),7.4 (br s, 12H, CH), 7.56 (br s, 8H, CH). FT-IR in KBr (in cm⁻¹); 3137,2925, 2574, 1626, 1526, 1434, 1275.

Example 4 Synthesis of Functionalized Nanomaterial (MNPs@Bpd)

The surface of the magnetite nanoparticles (MNPs) were decorated throughthe hydroxyl group functionalized dopamine. The obtainedbis(methyldiphenylphosphino) dopamine (bpd) ligand in anhydrous methanolwas sonicated with the suspended solution of magnetite nanoparticles inchloroform for 6 hours and produced a light black colored powder afterrepeated washings with methanol. The magnetite nanoparticles werefunctionalized (FIG. 2) by modifying a reported procedure [C. Duanmu, L.Wu, J. Gu, X. Xu, L. Feng and Xu Gu, Catalysis Communications 2014, 48,45—incorporated herein by reference in its entirety] as follows: 200 mgof magnetite nanoparticles were suspended in 10 mL of anhydrous CHCl₃ towhich a solution containing 200 mg of bis(methyldiphenylphosphino)dopamine in anhydrous methanol was added under argon. The mixture wassonicated for 6 h. The functionalized nanomaterials were collected withthe help of a strong magnet after washing repeatedly with methanol.

Example 5 Instrumentation

For solution nuclear magnetic resonance (NMR) analysis the ¹H and ¹³CNMR signatures were collected on a Joel INA/I-LA 500 Spectrometer andthe respective chemical shifts (δ) were defined using tetramethylsilane(TMS) as an internal standard. For the ³¹P NMR, 85% H₃PO₄ was used as aninternal reference. For the Fourier transform infrared (FT-IR) analysisthe IR spectra of the functionalized magnetic nanoparticles wereobtained from the Nicolet 720 in the range of 400 to 4000 cm⁻¹, usingKBr. For the thermal gravimetric analysis (TGA) the thermal analysis wasperformed on the Mettler-Tolledo with model TGA1 STAR^(e) System onaround 10 mg of dry samples under argon atmosphere with the heating rateof 10° C./min and with the temperature range of 0-800° C./min.

For X-ray diffraction (XRD) analysis the diffraction data was collectedon a Rigaku, model MiniFlex II diffractometer employing Cu-Kα radiation.The data was acquired over the 2θ range between 15 and 85. Forinductively coupled plasma mass spectrometry (ICP-MS) analysis thephosphorous content in the sample was determined by the ICP-MS (ThermoScientific, model XSERIES 2) by dissolving samples in concentrated HNO₃.

For scanning electron microscopy (SEM) and energy dispersivespectroscopy (EDS) analysis the surface morphology of the nanoparticleswas discerned by a field emission scanning electron microscope (FESEM,LYRA 3 Dual Beam, Tescan) operated at 30 kV. SEM samples were preparedeither from suspension or dry powder and coated with gold in anautomatic gold coater for 90 s. The energy dispersive X-ray spectra(EDS) for the chemical and elemental analysis of the nanoparticles werealso collected from the LYRA 3. For transmission electron microscopy(TEM) analysis the transmission electron imaging was done on a TEM(Joel, JEM 2011) operated at 200 kV with a 4k×4k CCD camera (Ultra Scan400SP, Gatan). The TEM samples were prepared by dropping on a coppergrid from an ethanolic suspension and drying at room temperature.

Example 6 Characterization of the Magnetic Nanoparticles (MNPs),Phosphinylated Ligand (Bpd) and Prepared Functionalized Nanomaterial(MNPs@Bpd)

The phosphinylated ligand (bpd) was characterized by ¹H and ³¹P nuclearmagnetic resonance (NMR) spectroscopy in deuterated dimethyl sulfoxide(DMSO-d₆). In the ¹H NMR, the shift of the CH₂—P proton at δ-4.14 ppmand its ethylene side chain was confirmed by the alkyl proton shift at2.49 and 3.69 ppm (FIG. 7). ³¹P NMR exhibited shift at δ-28.72 ppm (FIG.8) which is consistent with the literature data [P. Servin, R. Laurent,A. Romerosa, M. Peruzzini, J.-P. Majoral, and A.-M. Caminade,Organometallics 2008, 27, 2066; and O. Kuhl, S. Blaurock, J. Sieler andE. H. Hawkins, Polyhedron 2001, 20, 2171; and T. T. Co, S. C. Shim, C.S. Cho, T J Kim, S. O. Kang, W. S. Han, J. Ko, and C.-K. Kim,Organometallics 2005, 24, 4824—each incorporated herein by reference inits entirety]. The synthesized functionalized nanomaterials were imagedunder transmission electron microscope (TEM) analysis (FIG. 3B) andfound to be spherical and uniformly distributed. The typical core-shellstructures of the functionalized nanomaterial particles were confirmedwith spherical morphology and average diameter of 5-7 nm with thebis(methyldiphenylphosphino) dopamine ligand coating (FIG. 3C and FIG.3D). The crystalline nature of the magnetite nanoparticles wasascertained from their XRD signature (FIG. 4) which was identical tothat reported in the literature (JCPDS 2-1035), without the presence ofany other oxide or hydroxide phases. The broad diffraction peaksconfirmed the nanocrystalline nature of the material.

The presence of the bpd ligand on the surface of magnetite nanoparticleswas further characterized by the Fourier-transform infrared spectroscopy(FT-IR). The transmittance spectra of magnetic nanoparticles,bis(methyldiphenylphosphino) dopamine ligand, and the functionalizednanomaterial are shown in FIG. 5. All characteristic peaks of thedopamine compound were observed in the spectrum, in addition to thestrong appearance of the Fe—O vibration shift at 593 cm⁻¹. The presenceof 2930 cm⁻¹ (aromatic C—H stretching), 1628 cm⁻¹ and 1436 cm⁻¹ bandsclearly demonstrates the anchoring of the phosphinylated dopamine on thesurface of the particles. Thermal gravimetric analysis (TGA) studieswere conducted to investigate the thermal stability as well as thestrong attachment of the organic ligand on the magnetic nanoparticlesurface. The data showed that the weight loss at temperatures ≦150° C.was because of the loss of water molecules [J. Hee Yang, B. Ramaraj andK. R. Yoon, Journal of Alloys and Compounds 2014, 583, 128.—incorporatedherein by reference in its entirety]. The largest weight loss (˜9%)occurred between 200 and ˜450° C., which could be attributed to theelimination of ligands from the surface, in several steps. The amount ofbis(methyldiphenylphosphino) dopamine ligand on the surface was measuredby the phosphorous content. The ICP data yielded about 0.39 mmol ofphosphine/g of the functionalized nanoagents. This is the highest amountof phosphine loading on the surface of magnetite reported at this time,and may be attributed to the small size of the ligand. It is well knownthat steric and bulky moieties occupy less area on the surface and alarger number of ligands are thus able to bind through the phenolicoxygen to the Fe₃O₄ core.

Magnetization-field (M-H) curves recorded at room temperature areillustrated in FIG. 9. The superparamagnetic behavior for both samplesof the magnetite nanoparticles and synthesized functionalizednanomaterials. In addition, the presence of a very small paramagneticcomponent (saturation cannot be reached) was observed and deduced usingMicroMag software. It can be noted that the value of corecivity (H_(c))is very small within the range of 2.98-3.97 Oe, while the remanence(M_(r)) decreases slightly from 0.802 emu/g for the magnetitenanoparticles to 0.658 emu/g for the functionalized nanomaterials.Similarly to the remanence, the saturation magnetization (M_(s)) reducesslightly by ˜5 emu/g from the magnetite nanoparticles to the synthesizedfunctionalized nanomaterials. The above changes are attributed to theattached bis(phosphinomethyl) dopamine ligands on the surface of themagnetite nanoparticles.

Example 7 Catalytic Hydroformylation Reaction and Analysis

30 mg of the functionalized nanomaterial with 1 mmol of appropriatesubstrate was placed in anhydrous THF in a 45 mL Teflon-lined autoclave.The [Rh(NBD)Cl]₂ was added to this solution under argon. The sealedautoclave was purged 3 times with syngas (1:1 CO and H₂), pressurized upto 200 psi and kept at 90° C. for 16 h. After cooling to roomtemperature, the catalyst was magnetically extracted, washed severaltimes with dichloromethane and preserved for use in subsequent cycles.

The catalytic hydroformylation reaction was carried out on severalolefins (Table 1 and Table 2) in the presence of the syngas at differenttemperatures in a sealed autoclave at a pressure of up to 200 psi. FromTable 1, it is clear that the catalyst was very reactive and selectivetowards the branched aldehyde product in the low temperature regime. Areversal of selectivity was observed at high temperature for styrene,reaching up to ˜1.5. For example, the catalytic reaction was run at roomtemperature (rt) and 50° C. for 24 hours using RhCl₃ as the metalprecursor with styrene as the substrate in dry toluene, 35% and 100%conversion was observed with the selectivity of 0.20 and 0.47 withlinear to branched aldehyde respectively. In this reaction a fair amountof hydrogenated product was also observed, which could be attributed tothe lower solubility of RhCl₃ in toluene. This could mitigate theentrance of olefins into the hydroformylation catalytic cycles. When thereaction was carried out at 120° C., the linear aldehyde (a desiredproduct) was the major product.

Significant changes were observed when dimeric Rh(NBD) in freshlydistilled THF was used, the latter is considered a good solvent forhydroformylation over hydrogenation as it is reported to have led toformylation product at 90° C. [C. Duanmu, L. Wu, J. Gu, X. Xu, L. Fengand Xu Gu, Catalysis Communications 2014, 48, 45.—incorporated herein byreference in its entirety]. A series of substituted styrenes werestudied to determine the reactivity of catalyst towards the electronwithdrawing and electron donating groups in different positions of thearomatic ring but there was no significant difference observed [R.Abu-Reziq, H. Alper, D. Wang, and Michael L. Post, J. Am. Chem. Soc.2013, 128, 5279.—incorporated herein by reference in its entirety] andit is confirmed by entry 5 and entry 7 in Table 1. In addition, thereactivity of 3-nitro styrene, entry 8 in Table 1, was found to becomparatively higher with regards to selectivity among the series at thesame temperature.

Table 1. Hydroformylation^(a) of Olefins Using MNP@Bpd with the Pressureof 200 Psi Using [Rh(NBD)Cl]₂ as Metal Precursor

Time Temp Conversion^(b) Ratio^(c) Round # Substrate(s) (h) Solvent (°C.) (%) L B (L:B) 1^(d) Styrene 24 Toluene rt  35  6 29 0.20 2^(d)Styrene 24 Toluene  50 100 32 68 0.47 3^(d) Styrene 20 THE 120 100 60 401.50 4 Styrene 22 THF  90 100 48 52 0.92 5 4-Methylsyrene 19 THE  90 10050 42 1.19 6 4-Vinylanisole 18 THE  90 100 46 54 0.85 7 4-Chlorostyrene18 THF  90 100 56 44 1.27 8 3-Nitrostyrene 16 THF  90 100 57 43 1.32^(a)1 mmol of styrene in 10 mL anhydrous solvent under 200 psi pressurein presence of syngas (CO:H₂, 1:1) using 30 mg of catalyst^(b)determined by GC ^(c)determined by GC-MS ^(d)with RhCl₃

The functionalized nanomaterial or nanocatalysts were recycled (Table 2)after washing several times to remove all materials present after thefirst round of catalysis and recovered through the use of a magnet. Thenanocatalysts were recycled at the same temperature, pressure andduration and maintained significant activity even through a fourth roundof reactions. For entry 1 in Table 2, it was demonstrated that with theuse of the 30 mg of catalyst, the functionalized nanomaterial, and thecorresponding amount of [Rh(NBD)Cl]_(z) the selectivity ratio was 0.92and this trend persisted through the second round of reactions. However,in the third and fourth round of reactions the selectivity was reverseddue to unknown reasons.

TABLE 2 Recycling of Fe₃O₄@bpd@Rh of styrene as substrate forhydroformylation^(a) Conversion^(b) Ratio^(c) Round # Substrate(s) (%)Linear Branched (L:B) 1 Styrene 100  48 52 0.92 2 Styrene 97 43 54 0.793 Styrene 84 46 38 1.21 4 Styrene 69 38 31 1.23 ^(a)1 mmol of styrene in10 mL anhydrous freshly distilled THF at 90° C. under 200 psi pressurein presence of syngas (CO:H₂, 1:1) using 30 mg of catalyst for 22 h^(b)determined by GC ^(c)determined by GC-MS

Thus, the foregoing discussion discloses and describes merely exemplaryembodiments of the present invention. As will be understood by thoseskilled in the art, the present invention may be embodied in otherspecific forms without departing from the spirit or essentialcharacteristics thereof. Accordingly, the disclosure of the presentinvention is intended to be illustrative, but not limiting of the scopeof the invention, as well as other claims. The disclosure, including anyreadily discernible variants of the teachings herein, defines, in part,the scope of the foregoing claim terminology such that no inventivesubject matter is dedicated to the public.

The invention claimed is:
 1. A catalyst composition, comprising: afunctionalized nanomaterial, comprising; an iron oxide nanoparticlecore, and a bis(diarylphosphinomethyl) dopamine ligand, wherein thebis(diarylphosphinomethyl) dopamine ligand is anchored to a surface ofthe iron oxide nanoparticle core by phenolic hydroxide groups to form abis(diarylphosphinomethyl) dopamine ligand layer, and wherein thebisphosphine groups of the bis(diarylphosphinomethyl) dopamine ligandchelate at least one catalytic metal selected from the group consistingof nickel, platinum, palladium, rhodium, iron, silver, ruthenium andiridium.
 2. The catalyst composition of claim 1, wherein thefunctionalized nanomaterial is in the form of particles having anaverage diameter of 1-20 nm.
 3. The catalyst composition of claim 1,wherein the functionalized nanomaterial has a phosphine content of0.2-1.0 mmol per gram of functionalized nanomaterial.
 4. The catalystcomposition of claim 1, wherein the bis(diarylphosphinomethyl) dopamineligand layer covers greater than 70% of the surface of the iron oxidenanoparticle core.
 5. The catalyst composition of claim 1, wherein theiron oxide nanoparticle core comprises magnetite, Fe₃O₄.
 6. The catalystcomposition of claim 1, wherein the bis(diarylphosphinomethyl) dopamineligand is bis(diphenylphosphinomethyl) dopamine.
 7. The catalystcomposition of claim 1, wherein the bis(diarylphosphinomethyl) dopamineligand has the following structure (I):

wherein the aryl hydroxyl groups are deprotonated when anchored to thesurface of the iron oxide nanoparticle core, R₁, R₂, R₃ and R₄ are arylgroups, x and y are each independently from 1 to 10, and R₅-R₁₀ are eachindependently a halogen, an aryl group, a C₁-C₁₀ alkyl group, an alkoxylgroup, and a nitro group.